393721 has 2 divisors, whose sum is σ = 393722. Its totient is φ = 393720.

The previous prime is 393713. The next prime is 393727. The reversal of 393721 is 127393.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 318096 + 75625 = 564^2 + 275^2 .

It is a cyclic number.

It is not a de Polignac number, because 393721 - 2³ = 393713 is a prime.

It is equal to p₃₃₃₇₉ and since 393721 and 33379 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (393727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 196860 + 196861.

It is an arithmetic number, because the mean of its divisors is an integer number (196861).

2³⁹³⁷²¹ is an apocalyptic number.

It is an amenable number.

393721 is a deficient number, since it is larger than the sum of its proper divisors (1).

393721 is an equidigital number, since it uses as much as digits as its factorization.

393721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1134, while the sum is 25.

The square root of 393721 is about 627.4719117220. The cubic root of 393721 is about 73.2930609915.

The spelling of 393721 in words is "three hundred ninety-three thousand, seven hundred twenty-one".